This invention pertains to methods and therapeutic systems for treating a condition responsive to nicotine therapy, and particularly for smoking cessation. More specifically, this invention is directed to methods comprising the transdermal administration of nicotine, in combination with the transmucosal administration of nicotine to provide additional periodic doses of nicotine.
Nicotine replacement therapy as an aid to quitting smoking has been become increasingly popular. Nicotine chewing gum (nicotine polacrilex) and transdermal nicotine are two of the more popular forms of nicotine replacement available commercially. It has become clear, however, that the mere replacement of cigarettes with another nicotine source may not be sufficient to insure success in smoking cessation therapy. Specifically, conventional nicotine replacement therapy does not adequately address the symptoms associated with the cessation of smoking.
Of the many smoking withdrawal symptoms, craving for cigarettes is one of the most difficult to alleviate. As described in Steuer, J. D. and Wewers, M. E. in Oncology Nursing Forum 1989, 16, 193-198, cigarette craving is one of the most consistent, most severe, and earliest withdrawal symptoms experienced by those attempting to quit smoking. Some reports suggest that craving peaks over the first 24 to 72 hours of abstinence and then declines, although craving has been reported after five years of abstinence.
Research is focusing on the factors that precipitate craving in an attempt to better understand and deal with the problem of relapse. Some investigators believe that certain smokers are much more likely than others to experience craving symptoms, especially when trying to quit smoking. Based on literature reports and his own investigations, Harrington (in Br. J. Soc. Clin. Psychol. 1978, 17,363-371) reported that smokers can be separated by craving versus noncraving status, and that these separate populations have different responses to smoking cessation therapy.
Most commercially available products for nicotine replacement in smoking cessation therapy have not specifically addressed the issue of satisfying craving for nicotine. Instead, as mentioned above, they have generally been targeted towards providing a stable baseline level of nicotine in the blood. Some evidence indicates that low consistent blood levels of nicotine (as provided by transdermal nicotine, and to a lesser extent by nicotine gum) relieve some of the symptoms of nicotine withdrawal, but craving symptoms may not be among these (see Russell, M. A. H. in Nicotine Replacement: a Critical Evaluation; Pomerleau, O. F. and Pomerleau, C. S., Eds.; Alan R. Liss, Inc.: New York, 1988; pp 63-94). This may be because cigarette smoking provides an initial sharp rise in blood level, which is missing in these nicotine replacement therapies. The blood level peak produced by cigarettes is both higher (between 30-40 ng/mL) and sharper (this peak is attained within 10 minutes) than the steadier levels obtained from polacrilex gum or a transdermal system. Russell states that the optimal steady-state blood level for nicotine replacement is between 10-15 ng/mL, but that quick-rise effects are probably necessary for more complete relief from craving in the early stages of cigarette withdrawal. His investigations suggested that a rise in nicotine blood level of at least 10 ng/mL in 10 minutes is required to obtain postsynaptic effects at nicotinic cholinergic receptors in the central nervous system and at autonomic ganglia. These postsynaptic effects may be responsible for the feelings such as lightheadedness or dizziness experienced by cigarette smokers. See, also, Benowitz and Jacob (1984) Clin. Pharmacol. Ther. 36:265-270.
As mentioned above, nicotine gum (nicotine polacrilex) is one of the commercially available sources of nicotine for replacement therapy. This particular nicotine gum is actually an ion-exchange resin that releases nicotine slowly when the patient chews, and the nicotine present in the mouth is delivered directly to the systemic circulation by buccal absorption. However, much of the nicotine is retained in the gum through incomplete chewing or is largely wasted through swallowing, so that the systemic bioavailability of nicotine from this gum is low and averages only 30%-40%. Moreover, compared with cigarette smoking, this form of nicotine gum is a slow and inefficient source of nicotine. In addition, during ad libitum clinical or experimental use, the 2-mg gum produces steady-state blood nicotine levels that average around one third of the blood level peaks obtained from cigarette smoking. Thus, nicotine gum, when used alone, is frequently not effective as a method for smoking cessation.
Nicotine replacement through transdermal nicotine systems is another therapy that has become commercially available. These nicotine patches provide a low, consistent blood level of nicotine to the user, and bypass the first pass effects of the gut and liver. The concept of applying the teachings of transdermal drug therapy to the delivery of nicotine has been described in the literature, and particularly in U.S. Pat. Nos. 4,839,174, 5,135,753, and U.S. Pat. No. 4,943,435, herein incorporated by reference.
Nicotine is a suitable candidate for transdermal therapy because it is volatile, highly lipid soluble, and permeates the skin easily. It is, however, a reactive liquid and a strong solvent. Therefore, transdermal nicotine systems must be made of materials that are compatible with nicotine and can release nicotine at a safe, useful flux. In addition, these systems should be designed to exploit the benefits of controlled release transdermal therapy. In general, one of the recognized advantages of transdermal therapy as opposed to other drug administration techniques is the simplicity of the dosing regime. Another major advantage of continuous transdermal delivery is that the blood plasma levels of the delivered agent remain relatively steady. In this way, the periodic fluctuations between plasma levels above the safe threshold and below the efficacy threshold that are often seen with oral tablets or injections are eliminated, as are the "highs" associated with addictive substances.
The primary use of transdermal nicotine systems to date has been for smoking cessation therapy. A study by Rose, J. E. et al. (1985) Clin. Pharmacol. Ther. 38:450-456 demonstrated that systemic delivery of nicotine in pharmacologically useful amounts was feasible by the transdermal route. Studies using human cadaver skin in vitro are likewise consistent with this finding. Typical permeabilities during the first day of patch use are on the order of 0.1 mg/cm.sup.2 .multidot.h, increasing to 0.4 mg/cm.sup.2 .multidot.h and more at later times. Systemic absorption of 20 mg of nicotine (approximately equivalent to smoking one pack of cigarettes) per day would then be theoretically achievable with a dermal administration area of about 10 cm.sup.2. This surface area is well within the range of appropriate sizes for transdermal delivery systems.
In addition, human clinical studies by Dubois et al. (1989) Meth. and Find. Exp. Clin. Pharmacol. 11:187-195, for example, have demonstrated that application of transdermal nicotine systems results in nicotine blood levels on the order of 10-20 ng/mL, which is comparable to the minimum nicotine blood levels of moderately heavy cigarette smokers. Application of patches for 16 to 24 hours resulted in relatively constant blood levels in this range, indicating that the systems are useful for reliable long-term delivery of nicotine.
Several groups of investigators have described clinical studies that investigated efficacy and safety of transdermal nicotine systems for smoking cessation. Abelin et al. (1989) The Lancet 1:7-10 reported on the results of a double-blind study in which they determined that long-term use of a transdermal nicotine patch significantly increased the quit rate in cigarette smokers. The results of this study showed that the number of abstainers in the transdermal nicotine group after one, two, and three months of treatment was significantly greater compared to the placebo group. In another study reported by Mulligan et al. (1990) Clin. Pharmacol. Ther. 47:331-337, the use of a transdermal nicotine patch in a 6-week placebo-controlled double-blind study resulted in a significant degree of smoking cessation. Finally, a report by Rose et al. (1990) Clin. Pharmacol. Ther. 47:323-330 of a randomized double-blind trial indicates that certain smoking withdrawal symptoms were relieved by use of a transdermal nicotine system.
Therefore, transdermal nicotine systems can be designed to provide higher steady-state blood levels of nicotine, but are unable to provide blood level peaks or to provide a rapid increase in blood level. Thus, both nicotine gum and transdermal nicotine compete with each other as products providing steady-state nicotine blood levels, but do not satisfy craving symptoms for cigarettes in some smokers.
Other nicotine replacement products that are on the market or have been proposed in the literature have not been of serious interest in smoking cessation therapy, because of problems related to their use, and also because of limited ability to satisfy craving for cigarettes. Nicotine vapor has been delivered to patients in aerosol form, similar to the inhaler technology used to supply bronchial asthma medications, and in a "smokeless cigarette" such as that marketed by Advanced Tobacco Products under the trade name Favor.RTM..
Another smokeless version of nicotine delivered to the buccal mucosa is provided by chewing tobacco, oral snuff, or tobacco sachets. Tobacco sachets, which are especially popular in Scandinavia and the U.S., contain ground tobacco in packets that are sucked or held in the mouth.
The literature describes other capsules, tablets, and lozenges for oral delivery of nicotine. For example, WO 8803803 discloses a chewable capsule filled with a liquid containing 0.1-10.0 mg of nicotine, together with additives for improving flavor and dispersion. The capsules are provided in a variety of pH values to allow the patient a choice of nicotine absorption rate, and are especially intended as an aid to quitting smoking.
Another nicotine capsule formulation is disclosed by M. E. Jarvik et al. (1970) Clin. Pharm. Ther. 11:574-576 for ingestion as a smoking cessation aid. These capsules, however, were apparently swallowed whole by the subjects, according to the theory that intestinal absorption of nicotine could produce significant blood levels. The study showed a small but significant decrease in the number of cigarettes smoked by subjects, but no quantitative measurements of nicotine blood levels were obtained.
The literature also describes different designs of tablets for delivering nicotine to the mouth and digestive system. BE 899037 discloses a tablet containing 0.1 to 5 mg nicotine as a base or water-soluble acid salt as an aid for quitting smoking.
Wesnes and Warburton (1984) Psychopharmacology 82:147-150; and (1986) Psychopharmacology 89:55-59 discuss the use of nicotine tablets in experiments examining the effects of nicotine on learning and information processing. In the first experiment, nicotine was added to dextrose tablets with a drop of tabasco sauce added to disguise the taste of nicotine. In the second experiment, nicotine was added to magnesium hydroxide tablets, under the theory that an alkaline environment in the mouth would enhance buccal absorption. Again, tabasco sauce was added to the tablets to mask the taste of nicotine in both active and placebo tablets. The subjects were instructed to hold the tablets in the mouth for 5 minutes before swallowing, in order to maximize contact with the buccal mucosa.
Shaw (for example in GB 2142822 and U.S. Pat. No. 4,806,356) describes a nicotine lozenge prepared from a mixture of inert filler material, a binder, and either pure nicotine or a nicotine-containing substance by cold compression. WO 9109599 describes a nicotine product for oral delivery in the form of an inclusion complex of nicotine and a cyclodextrin compound. The patent also discusses the use of various excipients and direct compression for manufacture of the product.
In recent years, several nicotine lozenges have been commercialized and are available as over-the-counter products in the U.K. Resolution.RTM. lozenges, manufactured by Phoenix Pharmaceuticals and distributed by Ernest Jackson, contain 0.5 mg nicotine, together with the anti-oxidant vitamins A, C, and E. Stoppers.RTM. lozenges, distributed by Charwell Pharmaceuticals Ltd., contain 0.5 mg nicotine and are available in chocolate, orange and peppermint flavors.
To date, it has been difficult to deliver nicotine in a profile mimicking the nicotine blood levels achieved by consistent smoking, to satisfy cravings for nicotine in people who are attempting to quit smoking, and thus, to provide greater protection against relapse than other nicotine replacement therapies for people who are trying to quit smoking. It is therefore desirable to provide improved compositions and methods which avoid the disadvantages of these conventional nicotine delivery devices and methods while providing an effective means for delivering nicotine for smoking cessation treatment, for reducing nicotine craving, and for treating other conditions responsive to nicotine therapy.